Radionuclide imaging in interstitial lung disease.

The use of radionuclides to evaluate interstitial lung disease (ILD) has a long history. In the mid- and late 1970 s, it was appreciated that gallium uptake was seen in the lungs of patients with sarcoidosis or idiopathic pulmonary fibrosis. In both of these conditions, the amount of uptake seemed to correlate with other measures of inflammation in the lung. Gallium uptake was shown to predict response to therapy and persistent disease. However, several limitations to gallium scanning soon became apparent. The procedure is costly, it requires 48 to 72 hours for proper interpretation, and the uptake reverses quickly during corticosteroid therapy. The use of aerosol scanning with 99mTc-pentetic acid (DTPA) has also been shown to be useful in ILD. The clearance of 99mTc-DTPA aerosol is markedly increased in both sarcoidosis and other inflammatory lung diseases. However, the limitations of 99mTc-DTPA include the fact that cigarette smoking will also cause increased clearance. Therefore, the value of 99mTc-DTPA scanning value seems to be limited to nonsmokers. Several recent papers published on these and other techniques are reviewed here.